One in three working Americans might not be getting enough sleep, and it turns out that could be because of what they do for a living. Telephone switchboard operators, truckers, and people working on the railway, in health care, or the food business are more likely to be sleep deprived, a new study says. Airplane pilots and religious workers, on the other hand, tend to get plenty of shut-eye.

But being unconscious for a solid seven hours is often easier said than done: job stress, shift work, and physically demanding jobs can make it harder to get enough quality sleep when the workday is over. To understand if different jobs were linked to how much people slept, researchers with the Centers for Disease Control and Prevention analyzed telephone survey responses collected from nearly 180,000 working adults in 29 states.

They found that 36.5 percent of the people surveyed didn’t get enough sleep, and that, indeed, the work they did affected how much they slept, according to results coming out tomorrow in the CDC’s Morbidity and Mortality Weekly Report. Airplane pilots and religious workers were found to get the most sleep. (For pilots, that makes sense: in 2011, the Federal Aviation Administration changed pilots’ schedules to make sure that they’re not flying tired.) Teachers, librarians, farmers, and people working in fishing and forestry tend to get enough sleep, too; only about 31 percent reported getting less than seven hours a night.

On the other hand, more than half of the people working on phone switchboards and in certain kinds of transportation like trucking or rail travel got less than seven hours of sleep. About 40 percent of people working in factories, health care, food preparation, and emergency services were sleep deprived as well. All of these jobs have one thing in common: they tend to require people to work night shifts or odd hours. That throws off our internal biological clock, which tells us when we’re supposed to be sleepy — leading to less, and poorer quality, sleep.

It’s not just about the profession you have, of course

It’s not just about the profession you have, of course. The researchers also found that people who are not married or are separated from their spouses, are younger than 54, have some college education, or are black are also more likely to be sleep deprived.

The study has a pretty significant limitation: people self-reported how much sleep they were getting. And people can easily misremember, or mislead the researchers. For example, people who work in industries that regulate how much sleep you need (like pilots) might report more sleep than they’re actually getting, for fear of getting in trouble.

There are strategies that shift workers can use to get better — and possibly longer — sleep, like napping right before a night shift, eating well, and maintaining a consistent sleep schedule, the UCLA sleep center says. But that’s not always up to the employee — and employers really should make life easier by not rotating shifts at random. That’s not just good for the workers, but for the economy as a whole. A sleepy workforce costs the US about $411 billion each year in missed workdays. And who wants sleepy employees?